Electric generating system for automobiles and its control method

ABSTRACT

To provide a vehicle driving apparatus capable of providing a sufficient driving force. A driving high-power generator is driven by an engine. A DC motor is driven directly by energy from the generator. A driving generator output voltage control circuit controls output voltage of the generator in accordance with the demanded driving force from the vehicle to control the motor.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a vehicle driving apparatus for driving four wheels of the vehicle using an engine and an electric motor.

[0002] The conventional vehicle driving apparatus has been known, for example, from JP-A No. Hei 9-2090 (published in 1997), wherein a driving battery is utilized, and only at a low μ road for which start assistant is necessary, a 12-V alternator and a 12-V battery for ancillaries are combined to operate a motor. Further, as is known, for example, from JP-A No. Hei 7-231508 (published in 1995), which discloses a system for driving a motor in combination with a 12-V alternator and a 12-V battery for ancillaries.

[0003] However, the conventional system having, as a power source, a 12-V generator and a 12-V battery for ancillaries has a problem that electric energy that can be brought from the 12-V battery (for ancillaries) is small, and the period used for 4 WD running is limited so that for the continuous up-hills, high power need be supplied for a long period of time, failing to exhibit sufficient performance.

[0004] It is an object of the present invention to provide a vehicle driving apparatus capable of providing the sufficient driving force.

SUMMARY OF THE INVENTION

[0005] (1) To achieve the aforementioned object, the present invention provides a vehicle driving apparatus comprising: a first generator driven by an internal combustion engine, the first generator being provided separately from a second generator for ancillaries for supplying electric power to ancillaries of the vehicle; a motor directly driven by energy from the first generator; and control means for controlling output voltage of the first generator in accordance with a driving force requested from the vehicle to control the motor, wherein one wheels of front wheels and rear wheels of the vehicle are driven by the internal combustion engine while the other wheels of the front wheels and the rear wheels of the vehicle are driven by the motor.

[0006] With the constitution as described above, the exclusive-use generator and motor are used to obtain the sufficient driving force.

[0007] (2) Preferably, electric power supplied to the motor is supplied only from output of the first generator.

[0008] (3) Preferably, output voltage of the first generator is controlled by field current control of the first generator to control a driving force generated by the motor.

[0009] (4) Preferably, when electric power is not supplied to the motor, the first generator supplies electric power to other electric loads.

BRIEF DESCRIPTION OF THE DRAWUBGS

[0010]FIG. 1 is a system constitutional view showing the whole constitution of a 4-wheel drive vehicle using a vehicle driving apparatus according to one embodiment of the present invention;

[0011]FIG. 2 is a block diagram showing the constitution of the vehicle driving apparatus according to one embodiment of the present invention;

[0012]FIG. 3 is a system block diagram of a control system for the vehicle driving apparatus according to one embodiment of the present invention; and

[0013]FIG. 4 is a characteristic view of a high-power generator used in the vehicle driving apparatus according to one embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The constitution and operation of the vehicle driving apparatus according to one embodiment of the present invention will be described hereinafter with reference to FIGS. 1 to 4.

[0015] First, the whole constitution of a 4-wheel drive vehicle using a vehicle driving apparatus according to one embodiment of the present invention will be described with reference to FIG. 1.

[0016]FIG. 1 is a system constitutional view showing the whole constitution of a 4-wheel drive vehicle using a vehicle driving apparatus according to one embodiment of the present invention.

[0017] A 4-wheel drive vehicle 10 is provided with an engine 20 and a DC motor 30. The driving force of the engine 20 is transmitted to front wheels 26A, 26B through a transmission 22 and first axles 24A, 24B to drive the front wheels 26A, 26B. The driving force of the DC motors 30 is transmitted to rear wheels 36A, 36B through a clutch 32, a differential gear 33 and second axles 34A, 34B to drive the rear wheels 36A, 36B. When the differential gear 33 and the clutch 32 are connected, the rotating force of the DC motor 30 is transmitted to rear wheel axles 34A, 34B through the clutch 32 and the differential gear 33 to drive the rear wheels 36A, 36B. When the clutch 32 is disengaged, the DC motor 30 is mechanically separated from the rear wheels 36A, 36B, so that the rear wheels 36A, 36B do not transmit the driving force to the road surface. For the DC motor, for example, a DC shunt-wound motor which is easily switched from a forward operation to a reverse operation and vice versa or a separately excited DC motor is used.

[0018] While in the foregoing, a description has been made of the 4-wheel drive vehicle in which the front wheels 26A, 26B are driven by the engine 20, and the rear wheels 36A, 36B are driven by the DC motor 30, it is noted that the front wheels may be driven by the DC motor, and the rear wheels may be driven by the engine, and further, it can be also applied to vehicles in excess of 6-wheel such as a truck, and traction vehicles such as a trailer.

[0019] Within the engine room are arranged a generator for ancillaries (ALT1) 40 for performing normal charging and generation system and a battery for ancillaries 42, and output of the generator for ancillaries 40 belt-driven by the engine 20 is stored in the battery for ancillaries 42. Further, a driving high-power generator (ALT2) 44 belt-driven by the engine 20 is disposed in the vicinity of the generator for ancillaries 40. The DC motor 30 is driven by output of the driving high-power generator 44. The generator 40 is, for example, a general generator of about 12 V, 2 kW, and the driving high-power generator 44 is a generator capable of obtaining higher power than that of the generator for ancillaries 40, for example, a generator of about 36 V, 6 kW.

[0020] Output of the engine 20 is controlled by an electronically controlled throttle valve 52 driven by a command issued from an engine control unit (ECU) 50. The electronically controlled throttle valve 52 is provided with an accelerator opening-degree sensor 54 to detect an opening-degree of the accelerator. Where an accelerator pedal of a mechanical link and a throttle valve are used in place of the electronically controlled throttle valve, an accelerator opening-degree sensor can be provided on the accelerator pedal. Further, ECU 50 controls the transmission 22. The transmission 22 is an automatic transmission, which is automatically controlled so as to provide a gear ratio selected by a selection lever 23. The position of the selection lever 23 is detected by a gear position detection sensor 25. It is noted that the transmission 22 may be a manual transmission.

[0021] Brakes 28A, 28B, 38A and 38B provided on the front wheels 26A, 26B and the rear wheels 36A, 36B, respectively, are provided with anti-lock brake (ABS) actuators 29A, 29B, 39A and 39B controlled by an anti-lock brake (ABS) control unit 55. Further, the front wheels 26A, 26B and the rear wheels 36A, 36B, respectively, are provided with rotation. sensors 56A, 56B, 58A and 58B for detecting the rotational speed and the rotational direction. The rotation sensors 56A, 56B, 58A and 58B are provided every wheel, but may be disposed on one of or both the front wheel axle and the rear wheel axle.

[0022] A driving generator output voltage control circuit (GCU) 60 calculates vehicle speeds on the basis of the rotational speed of the wheels 26A, 26B, 36A and 36B detected by the rotation sensors 56A, 56B, 58A and 58B, and controls the driving high-power generator 44 and the DC motor 30 on the basis of the calculated vehicle speeds. The details of the control by the GCU 60 will be described referring to FIG. 3.

[0023] In the following, the constitution of the vehicle driving apparatus according to the present embodiment will be described with reference to FIG. 2. FIG. 2 is a block diagram showing the vehicle driving apparatus according to one embodiment of the present invention, showing an example of circuits for power supply and controls. The same reference numerals as those of FIG. 1 indicate the same parts. In the figure, with respect to the connection between the blocks, the solid line indicates a connection of power supply, and the broken line indicates a connection for controls. Input into an output voltage control circuit for a driving generator (GCU) 60 are information on the rotational speed and rotational direction of the wheels 26A, 26B, 36A, 36B detected by the rotation sensors 56A, 56B, 58A and 58B, information on an accelerator opening-degree detected by the accelerator opening-degree sensor 54, and information on the gear position detected by the gear position detection sensor 25.

[0024] GCU 60 outputs the command value of output voltage to the driving high-power generator (ALT2) 44 to control the output voltage of the high-power generator 44 so that the DC motor 30 is controlled. GCU 60 controls a field current to flow into a field winding 31 of the DC motor 30 so as to directly control the DC motor, thus improving the lowering of response resulting from that the DC motor 30 is controlled by the high-power generator 44.

[0025] The driving generator output voltage control circuit (GCU) 60 is provided with an I/O circuit 61, an A/D converter 62, a micro processor (MPU) 63, an I/O circuit 64, a H bridge driver 65 and a H bridge circuit 66. Gear position information detected by the gear position detection sensor 25 is fetched into the MPU 63 through the I/O circuit 61. Information of the rotational speed and rotational direction of the wheels 26A, 26B, 36A, 36B detected by the rotation sensors 56A, 56B, 58A and 58B, and information of an accelerator opening-degree detected by the accelerator opening-degree sensor 54 are fetched into the MPU 63 through the A/D converter 62. The MPU 63 is provided with a memory for holding programs and data for controlling the CPU and the motor, calculates vehicle speeds in accordance with the input information, calculates output voltage value of the driving high-power generator 44 to supply it from the I/O circuit 64 to the driving high-power generator (ALT2) 44, to control the output voltage value generated. The MPU 63 regulates a field current flowing into the field winding 31 of the DC motor 30 in the H bridge circuit 66 through the H bridge driver 65. When the vehicle is moved back, a field circuit is caused to flow in the direction opposite to that of the forward operation by the H bridge circuit 66 to obtain the reverse driving force similar to that of the advance of the vehicle. Further, the MPU 63 produce connection and disconnection signals for the clutch 32 to feed it from the I/O circuit 64 to the clutch 32.

[0026] While in the foregoing, each sensor signal is directly input into the driving generator output voltage control circuit 60, it is noted that the signal may be available via an in-vehicle LAN (CAN) from the control units with the sensor amount loaded (for example, such as ECU 50 and ABS control unit 55).

[0027] The battery for ancillaries 42 is a 12-V battery, which constitutes a normal charge-discharge system between the generator for ancillaries 40 and various electric loads associated with the 12 V power supply. The field-side power supply for the DC motor 30 and the driving high-power generator 44 is supplied from the generator for ancillaries 40 and the battery for ancillaries 42. Two power supply systems are provided to thereby enable controlling by a method for controlling a field current of the driving high-power generator 44 and a method for controlling a field current of the DC motor. For example, when the necessary rotational frequency of the motor when the vehicle starts is low and the required torque is high, the output current value of the driving high-power generator 44 is set to a greater value whereby the motor assumes the low rotation and the output of high torque. When the necessary rotational frequency of the motor when the vehicle is running is high and the required torque is low, the output current value of the driving high-power generator 44 is set to a greater value to enable coping with the situation. Further, the field current of the DC motor 30 is lowered whereby the rotational frequency of the motor can be increased while improving the responsiveness when the vehicle runs. When a value demanded for torque distribution is higher in the front wheel 26 than in the rear wheel 36, the field current value of the driving high-power generator 44 is lowered to enable making the torque distribution of the front wheel 26 and the rear wheel 36 variable.

[0028] The power supply line of the clutch 32 is connected to the battery for ancillaries 42, and the connection and disconnection of the clutch 32 are controlled by the MPU 63 whereby when the 4-wheel drive function is not necessary, the mechanical connection between the rear wheels 36A, 36B and the DC motor 30 can be forcibly disengaged without depending on the constantly changing generative force of the driving high-power generator 44. For example, when the vehicle speed assumes 20 km/h, the clutch 32 is turned OFF to provide the driving system for only the front wheels whereby the abrasive amount of the brush of the DC motor 30 can be reduced as compared to the system which operates in the whole vehicle speed region. Further, in the state that the clutch 32 is disengaged, the DC motor 30 is not used. Thus, the driving high-power generator 44 is switched by a switch to enable using as a charging device and a power supply for other ancillaries.

[0029] Further, the motor 30 is utilized as a generator at the time of high speed traveling and on the downhill, and equipment for charging or consuming generation provided by the motor 30 is provided within the vehicle to thereby obtain the braking force such as regenerative braking and generative braking.

[0030] The operation of the vehicle driving apparatus according to the present embodiment will be described with reference to FIGS. 3 and 4. FIG. 3 is a system block diagram of a control system of the vehicle driving apparatus according to one embodiment of the present invention; and FIG. 4 is a characteristic view of a high-power generator used in the vehicle driving apparatus according to one embodiment of the present invention. In FIG. 3, the same reference numerals as those of FIGS. 1 and 2 indicate the same parts.

[0031] As shown in FIG. 3, it is supposed that a wheel driven through the transmission 22 by the driving force of the engine 20 be, for example, the front wheel 26, and a wheel driven by the DC motor 30 be the rear wheel 36.

[0032] Here, the contents of controlling and processing of GCU 60 will be described.

[0033] In Step a10, the GCU 60 processes so that the low speed side assumes vehicle speed to calculate the vehicle speed on the basis of the rotational speed information of the front and rear axles input from the rotation sensors 56A, 56B, 58A and 58B.

[0034] Then, in Step a20, the GCU 60 calculates the motor driving torque required in response to the running state judged in Step s10.

[0035] Then, in Step a30, the GCU 60 calculates the voltage command value for the driving generator 44 so as to obtain the motor driving torque calculated, to output it to the driving generator 44. The driving generator 44 performs the feedback control so that the output voltage assumes a command value, to output the output voltage V to the DC motor 30. Real torque T of the DC motor 30 is input into the rear wheel 36 by the voltage V to assume the state of providing the actual wheel speed, and the feedback control of the whole system is carried out.

[0036] Next, the characteristics of the high-power generator will be described with reference to FIG. 4. In FIG. 4, an output voltage is the output voltage of the high-power generator 44, which output voltage can be contemplated as an input voltage of the DC motor 30 if a wiring resistance is excluded.

[0037] When necessary torque is high and the vehicle speed is low such as when the vehicle starts or when getting out of a rut, the output of the generator 44 is controlled so that the points of V2 and I2 which are high in current value to the motor 30 and relatively low in voltage value in FIG. 4 are used. Further, where the vehicle speed is low, for example, 15 to 20 km/h, some torque T is transmitted to the rear wheel 36, and the motor 30 is synchronized with the rotational frequency of the rear wheel 36 through a reduction gear. Thus, the output of the generator 44 is controlled so that the points of V1 and I1 which are relatively low in current value to the motor and relatively high in voltage value are used.

[0038] Further, when the demand value of power higher than that in the characteristics of FIG. 4 is present, the field current of the generator 44 and the motor 30 is controlled within the allowable range of the generator 44, the motor 30 and the battery 42 to enable driving the motor 30 in the range of higher power and lower power.

[0039] As described above, according to the present embodiment, since the sufficient driving force can be secured by directly driving the motor by the exclusive-use generator, the driving performance is obtained sufficiently in comparison with that of the so-called mechanical 4 WD. Further, there can be provided advantages of the original electric 4-drive (such that a propeller shaft is unnecessary, and a floor shape of the vehicle can be made flat). Further, since no battery is necessary, the cost is low, the layout in the vehicle is advantageous, and maintenance and replacement of batteries are unnecessary, resulting in simple and efficient construction and in realizing the driving apparatus having the sufficient performance. 

What is claimed is:
 1. A vehicle driving apparatus comprising: a first generator driven by an internal combustion engine, the first generator being provided separately from a second generator for ancillaries for supplying electric power to ancillaries of the vehicle; a motor directly driven by energy from the first generator; and control means for controlling output voltage of the first generator in accordance with a driving force requested from the vehicle to control the motor, wherein one wheels of front wheels and rear wheels of the vehicle are driven by the internal combustion engine while the other wheels of the front wheels and the rear wheels of the vehicle are driven by the motor.
 2. The vehicle driving apparatus according to claim 1 , wherein electric power supplied to the motor is supplied only from output of the first generator.
 3. The vehicle driving apparatus according to claim 1 , wherein output voltage of the first generator is controlled by field current control of the first generator to control a driving force generated by the motor.
 4. The vehicle driving apparatus according to claim 1 , wherein when electric power is not supplied to the motor, the first generator supplies electric power to other electric loads. 